The sacrament of communion
A Catholic is one who practices Catholicism.
One practice that was not a source of contention between the Catholic Church and Martin Luther was the belief in the Holy Trinity. Both the Catholic Church and Lutherans agreed on the doctrine of the Trinity, which states that there is one God in three persons: Father, Son, and Holy Spirit. This was not a matter of dispute during the Protestant Reformation.
As you are not listing any of the possible "practices" in your question, I'm just going to take a stab in the dark; for instance, infant baptism was never a source of contention. Initially indulgences were not a source of contention (Luther was only objecting to the people's misunderstanding of indulgences), but later he rejected the entire system. One user said that the sacrament of communion was often an answer that they were looking for when this question is asked on a test, but Martin Luther most definitely did not believe in transubstantiation, he believed in consubstantiation. 1_ the sacrament of communion
As you are not listing any of the possible "practices" in your question, I'm just going to take a stab in the dark; for instance, infant baptism was never a source of contention. Initially indulgences were not a source of contention (Luther was only objecting to the people's misunderstanding of indulgences), but later he rejected the entire system. One user said that the sacrament of communion was often an answer that they were looking for when this question is asked on a test, but Martin Luther most definitely did not believe in transubstantiation, he believed in consubstantiation. 1_ the sacrament of communion
As you are not listing any of the possible "practices" in your question, I'm just going to take a stab in the dark; for instance, infant baptism was never a source of contention. Initially indulgences were not a source of contention (Luther was only objecting to the people's misunderstanding of indulgences), but later he rejected the entire system. One user said that the sacrament of communion was often an answer that they were looking for when this question is asked on a test, but Martin Luther most definitely did not believe in transubstantiation, he believed in consubstantiation. 1_ the sacrament of communion
Opium
Opium
It depends on the particular conflict, but the two territories most in contention between the Israelis and Palestinians are the Gaza Strip and the West Bank (including East Jerusalem). There is much contention between Israelis and Syrians over the Golan Heights and between Israelis and Lebanese there is some contention over the Shebaa Farms and the area south of the Litani River.
Yes, the issue of priestly celibacy is a point of contention between the Eastern Orthodox and Roman Catholic Churches. In the Eastern Orthodox Church, married men can become priests, while the Roman Catholic Church requires celibacy for priests. This difference has been a historical source of tension between the two churches.
I believe you are looking for the phrase "bone of contention". I'm not sure the origin, but I imagine it has something to do with animals fighting over a bone. that's completely wrong, the phrase is 'bone of contention' but it means to have a problem with someone or something. if i failed to pay back money to an old friend it would always be a bone of contention between us. but it can apply to anything
Christianity was split between the roman catholic church and the eastern orthodox church